The present invention relates to a thermoelectric unit for the cooling or heating of a fluid. This thermoelectric unit can be installed through an opening in a wall and is suited, in particular but not exclusively, for providing cooling for a refrigerating apparatus.
In thermoelectric systems, one or more flat board like semiconductor devices generally known as thermoelectric coolers (TECs) transfer heat according to the Peltier effect. A direct electrical current is applied to the semiconductor device which results in a corresponding transfer of heat from one side of the semiconductor device to the other, thereby creating a cold side and a hot side.
TEC based thermoelectric systems address environmental concerns given the complete absence of a requirement for the use of heat transfer fluids such as Freon(trademark), required in more conventional evaporating/condensing type units, while at the same time providing a lighter, more reliable and potentially less expensive apparatus. Moreover, TEC based thermoelectric systems provide for a substantial reduction in maintenance costs due to their simplicity of construction and limited number of parts. This is particularly true in the case of movable commercial apparatuses where fluid leakage frequently occurs requiring extensive and costly preventive maintenance. Also, ongoing improvements in TECs"" construction and control are providing coefficient of performance (COP) figures competing with those of conventional thermodynamic systems, especially when start/stop and defrost cycles are taken into account.
Several systems have been developed over the years using a TEC device for providing the cooling required by refrigerating apparatuses, while providing numerous advantages over evaporating/condensing type units. However, use of thermoelectric units has never been contemplated in large refrigerating units such as grocery store refrigerators and coolers. Moreover, thermoelectric units are usually an integral part of the cooling or heating apparatus with few thermoelectric units being assembled in a stand-alone configuration. Of those that are assembled as complete stand-alone units, these are not designed for easy installation on an insulated wall and removal therefrom as one or more complete units.
There are many advantages to a modular concept for the thermoelectric units. For instance, the units can be easily retrofitted into existing refrigerators and coolers, providing a conversion path to solid state operation, and they can be replaced quickly in case of malfunction. Also, many small units can be used, distributed along large open-top coolers, to provide uniform spreading of the cooling capacity without requiring the addition of expensive runs of finned tubing requiring extensive maintenance (cleaning) to maintain maximal efficiency and heat transfer capacity.
A refrigeration unit implementing a number of Peltier effect devices is disclosed in U.S. Pat. No. 5,784,890 by Polkinghorne and issued on Jul. 28, 1998. As disclosed, the cooling unit requires a coolant reservoir and circulation system, cannot be easily retrofitted into an existing refrigeration apparatus and is complex and expensive to manufacture. It provides local cooling and was not designed in a manner allowing the co-operative use of multiple units to provide uniform cooling throughout the entire volume of a large refrigerating enclosure.
A thermoelectric cooling unit comprised of a Peltier effect device sandwiched between two heat sinks is disclosed in U.S. Pat. No. 5,315,830, issued to Doke et al. on May 31st, 1994. The unit as disclosed is designed to be assembled into a specially designed opening provided in the wall of a moulded plastic cooler. This cooling unit is unsuited for installation through a thick insulated panel of an existing or conventional commercial cooler given the small spacing between the hot and cold heatsinks. Furthermore, the fan on the cold side is not compatible with such an application, with the shaft acting as a conduit for moisture and providing a heat bridge between the cold and hot sides.
Similarly, the thermoelectric cooling unit disclosed in U.S. Pat. No. 5,699,669 by Gebhard and issued on Dec. 23rd, 1997, is used in a water cooler and assembled through a circular hole provided in the bottom wall of the reservoir. The unit has a threaded cylindrical cold side probe which is inserted through the hole following which a threaded mating ring is screwed thereon. Although this structure is practical in nature, it requires some adaptation in order to be used through a thick wall with its cold side exchanging heat with a gaseous environment for use in a refrigerator or cooling container. Moreover, the performance requirements for the disclosed water cooling application are far less critical than those applicable when providing refrigeration for a large subzero box cooler as contemplated in the present invention.
Although the above examples show that some modular thermoelectric cooling units exist, these thermoelectric cooling units are nevertheless lacking important features necessary for them to be useful as a readily installed modular unit for providing cooling within a thick walled enclosure. Also, no practical solution is provided in the prior art for the conversion of large elongated refrigerators, coolers or temperature holders of the type used in supermarkets to solid state cooling.
There is thus a need for a pre-assembled modular thermoelectric cooling unit which can be installed easily and rapidly through a thick insulated wall to provide cooling on one side of said wall and dissipate heat on the other side thereof. A plurality of such units are suitable for advantageously converting large refrigerating apparatuses to solid-state cooling, according to illustrative structures as contemplated in the present invention.
An object of the present invention is to provide a modular thermoelectric u nit which overcomes the above discussed limitations and drawbacks.
More specifically, in accordance with the invention as broadly claimed, there is provided a modular thermoelectric cooling/heating unit for installation through an opening in a wall separating first and second temperature zones. The wall has a given thickness and the modular thermoelectric cooling/heating unit comprises (a) a thermoelectric device for connection to an electrical power supply, this thermoelectric device comprising a cold surface and a hot surface, (b) a heat conducting block having a proximal end for thermally contacting with a first of the cold and hot surfaces of the thermoelectric device, and a distal end, (c) a first heatsink for thermally contacting with a second of the cold and hot surfaces, (d) a second heatsink for thermally contacting with the distal end of the heat conducting block, and (e) a thermally insulating housing for covering at least a portion of the heat conducting block between the proximal and distal ends of the heat conducting block. In operation, the first heatsink is located in the first temperature zone, at least a portion of the heat conducting block and the thermally insulating housing extend through the wall opening, and the second heatsink is located in the second temperature zone.
In accordance with illustrative embodiments:
at least a portion of the second heatsink is integral with the distal end of the heat conducting block;
the thermoelectric device comprises at least one Peltier effect device;
the thermoelectric cooling/heating unit further comprises insulating material within the thermally insulating housing being in close contact with the surface of the heat conducting block;
the modular thermoelectric cooling/heating unit further comprises a fan member associated with at least one of the first and second heatsinks to improve heat transfer;
the heat conducting block has a length sufficient to extend through the thickness of the wall;
the heat conducting block and the thermally insulating housing are substantially cylindrical and co-aligned along an axis substantially perpendicular to the wall;
the first heatsink has a base and the thermally insulating housing has a proximal portion for connection to the base of the first heatsink, and the thermally insulating housing has a threaded distal portion to receive a threaded ring and firmly retain the modular thermoelectric cooling/heating unit in the wall opening;
the thermoelectric cooling/heating unit further comprises an annular sealing spacer inserted between the threaded ring and the wall;
the annular sealing spacer is an annular wedge-shaped sealing spacer;
the modular thermoelectric cooling/heating unit further comprises a display of a status of the thermoelectric device; and
the first surface of the thermoelectric device has a first area, the heat conducting block has a cross section with a second area larger than the first area, and the proximal end of the heat conducting block has a pyramidal shape to adapt the first area of the first surface of the thermoelectric device to the second area of the cross section of the heat conducting block.
The present invention also relates to a modular cooling system for installation onto a refrigeration unit having a fluid circulation conduit with an inlet and an outlet. This modular cooling system comprises at east one modular thermoelectric cooling/heating unit as defined hereinabove, installed through an opening in a wall of the refrigeration unit, wherein the first and second surfaces of each thermoelectric device are the cold and hot surfaces of the thermoelectric device, and wherein each second heatsink of the at least one modular thermoelectric cooling/heating unit is located within the fluid circulation conduit such that fluid entering the inlet is drawn over each second heatsink such that the temperature of the fluid at the outlet is below the temperature of the fluid at the inlet.
The modular cooling system may further comprise a controller unit, operationally connected to the electrical power supply and responding to operating conditions of the modular cooling system, this controller unit comprising a monitoring subsystem for monitoring a temperature within the refrigeration unit, a temperature of the at least one second heatsink and a voltage and a current across the at least one thermoelectric device, and a thermostatic controller for varying the current across the at least one thermoelectric device in response to fluctuations in temperature determined by the monitoring subsystem.
According to other illustrative embodiments:
the controller unit further comprises a maintenance control subsystem operationally connected to the at least one thermoelectric device for providing continuous display of a status of the at least one thermoelectric device;
the controller unit further comprises a communication interface for remote monitoring and modification of the operating conditions;
the controller unit further comprises a defrost system producing defrost cycles by reversing the voltage across the at least one thermoelectric device;
the wall is a bottom wall or a side wall of the refrigeration unit;
the at least one modular thermoelectric cooling/heating unit is installed through an opening of a side wall of the refrigeration unit and each first heatsink of the at least one modular thermoelectric cooling/heating unit includes a plurality of heat radiating fins extending generally vertically to facilitate natural convection;
each first heatsink of the at least one modular thermoelectric cooling/heating unit is located within an air conduit, advantageously a generally vertical air conduit; and
the fluid comprises a gaseous fluid.
The present invention further relates to a cooling/heating system comprising a housing, a thermally insulating partition, at least one thermoelectric cooling/heating unit as described hereinabove, and first and second fluid circulating members. The thermally insulating partition is situated in the housing to divide that housing into first and second conduits, the first conduit comprising a first inlet and a first outlet and the second conduit comprising a second inlet and a second outlet. The thermoelectric cooling/heating unit(s) are installed through an opening(s) in the thermally insulating partition with the first heatsink(s) located in the first conduit and the second heatsink(s) located in the second conduit. The first fluid circulating member is associated to the first conduit and produces a first fluid stream in the first conduit from the first inlet to the first outlet whereby heat exchange is conducted between the first fluid stream and the first heatsink(s). The second fluid circulating member is associated to the second conduit and produces a second fluid stream in the second conduit from the second inlet to the second outlet whereby heat exchange is conducted between the second fluid stream and the second heatsink(s).
The foregoing and other objects, advantages and features of the present invention will become more apparent upon reading of the following non restrictive description of illustrative embodiments thereof, given for the purpose of illustration only with reference to the accompanying drawings: